1. Field of the Invention
The present invention relates to a composite of metal oxide nanoparticles and carbon, a method of production thereof, an electrode and an electrochemical element that employ this composite.
2. Description of Related Art
A carbon material etc. that stores and releases lithium is currently used as the electrode for lithium batteries, but there is a risk of decomposition of the electrolytic solution since the negative potential is lower than the reductive decomposition potential of hydrogen. Accordingly, as described in Patent Documents 1 or 2, the use of lithium titanate having higher negative potential than the reductive decomposition potential of hydrogen is being investigated, but lithium titanate has a problem of low output property. Accordingly, attempts are being made to improve output property by an electrode in which lithium titanate is made into nanoparticles and supported on carbon.
The inventions described in these Patent Documents are methods for applying sheer stress and centrifugal force to a reactant in a rotating reactor to allow promotion of chemical reaction (generally referred to as mechanochemical reaction), thereby yielding dispersed lithium titanate supported on carbon. In this case, for example, titanium alkoxide and lithium acetate which are the starting materials of lithium titanate, a carbon such as carbon nanotube or Ketjen Black, and acetic acid etc. are used as reactants.
Although the electrodes that use carbon supporting lithium titanate nanoparticles described in these Patent Documents exert superior output property, there are recent demands to further improve the output property and to improve the electric conductivity in this type of electrode.
There are also demands to produce a composite in which not only lithium titanate nanoparticles but other metal oxide nanoparticles are supported on carbon, and thereby obtain an electrode or an electrochemical element having a more superior output property. In particular, the use of a metal oxide cheaper than lithium such as manganese oxide is desired.
The present invention is proposed to solve the problems of the conventional technology as stated above, the object of which is to provide a composite of metal oxide nanoparticles and carbon that can yield an electrode or an electrochemical element that enables improvement of output property and electric conductivity, as well as a method of production thereof. In addition, another object of the present invention is to provide an electrode and an electrochemical element that employ said composite.